X-Axis

Logarithmic

Y-Axis

Logarithmic

Y-Axis 2

Logarithmic

Policy

Climate

Economy

Choose among four types of policies. Business as usual assumes
that there are no controls on CO2 emissions. Choosing an
optimized policy allows the computer to choose an emissions
reduction plan that maximizes welfare (measured by the present value
of utility). A simulated carbon tax allows you to pick a
global tax rate on emissions for each of three periods. A climate
treaty allows you to choose emissions reductions from a
2005 baseline for each of three target dates and the portion of
world emissions that are subject to the treaty.

Business as usual

Optimized policy

Be aware that optimized policies can take about ten
seconds to run, depending on your input parameters—and a bit longer
longer if you’re using a BEAM carbon cycle.

Emissions reduction(% 2005 emissions)

Participation(% of globe)

20501000100

&bullet;

21001000100

&bullet;

21501000100

&bullet;

How bad climate change will be? Climate sensitivity is a measure
of how much temperatures will increase as we increase CO2
in the atmosphere. A higher sensitivity means a greater temperature
increase for a given level of emissions. Harms determines how
much those temperature increases hurt people and the economy.
A higher value means that harms increase faster as temperatures
increase.

Climate sensitivityless than expectedmore than expected

How much will temperatures go up? Or: how much will temperature
increase in degrees C from a doubling of atmospheric CO2?

Harmsless harmmore harm

How large will the harms to the climate be, due to an increase
in temperatures?

How will the economy perform without climate change? Growth
determines how fast the economy grows. A higher value means that the
economy grows more quickly. Energy efficiency determines how
much CO2 the economy produces for a given level of output.
A higher value means that the economy becomes energy efficient over
time more quickly. Cost of clean energy determines how much it
costs to replace fossil fuels with clean energy such as solar or
wind. The model assumes that the costs of clean energy goes down
over time. A higher value means that the costs decline slowly so that
clean energy is more expensive.

Growth (%)
slower growthfaster growth

Decline in the rate of growth in productivity over time.

Energy efficiency (%)
less energy efficientmore energy efficient

Reduction in energy intensity per decade. Or the rate of decline
in energy use per $ of GDP.

Cost of clean energyless expensivemore expensive

The rate of decline in costs of reduction emissions—hpw fast will
these costs decline over time?

webDICE is built and maintained by the Center for
Robust Decision Making on Climate and Energy Policy at the University
of Chicago. Questions and comments should be directed to
info-rdcep@ci.uchicago.edu.

Warning

The parameters you chose produce a result that is physically
impossible. This can occur because climate change causes harms
that are sufficiently bad that the economy is forced to operate
below subsistence levels. It may also occur because you have
specified emissions reductions that are greater than the emissions
from the participating countries. webDICE does not contain the
flexibility to predict what might happen as we approach these
circumstances so it continues to produce the graphs under the
parameters you chose.

Although the results are not physically possible, it does not mean
that they are not meaningful. webDICE is telling you that under the
parameter choices you made, something very extreme will happen:
the population will have to shrink because the economy cannot support
the full population, or the emissions reductions cannot be achieved
with the participation rates. The particular results in the graphs,
however, are not meaningful.